Wide temperature range friction and wear properties of NbMoWTa-Al2O3 solid lubricated composites
A novel NbMoWTa refractory high entropy alloy-based solid lubricated composite was prepared by high-energy ball milling and spark plasma sintering.The effect of nano-Al2O3 as a solid lubricant on the tribological properties of NbMoWTa refractory high entropy alloy in wide temperature range was systematically studied.The results show that the nano-Al2O3 particles are uniformly dispersed at the grain boundary and within the grains of the matrix phase of NbMoWTa refractory high entropy alloy with BCC structure,and the microhardness of NbMoWTa is significantly increased caused by strong dispersion strengthened.The nano-Al2O3 particles have a significant effect in reducing the coefficient of friction and wear from room temperature to 800℃.At room temperature,additing sufficient nano-Al2O3 can improve the wear resistance of the composites due to the significant increase in microhardness.At medium and high temperatures,the continuous dense oxidized tribo-layer formed on the surface of the composite plays a critical role in improving the tribological properties.Nano-Al2O3 particles assist the oxidized tribo-layer to carry a larger load,improve its compactness and stability,and thus protect the matrix more effectively.In addition,the existences of nano-Al2O3 particles can inhibit the excessive volatilization of MoO3 at 800℃.
refractory high entropy alloysolid-lubricating compositesoxidized tribo-layernano-Al2O3
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